A PROCESS FOR MANUFACTURING NULLITE AGGREGATES FROM PYROPHILLITE AND AL-HYDROXYHYDROGEL

摘要

A process for manufacturing mullite aggregates from pyrophillite an apparently unusable mineral to produce quality mullite aggregate (of the order of 35% mullite). Pyrophyllite, an alumino silicate mineral, abundantly available in nature finds very limited use in refractory industry. Theoretically, pyrophyllite on heating yields mullite, but this reaction is retarded due to the formation of large amount of free silica and slumino-silicate glassy phase. A process has been provided to produce mullite aggregates from a powder precursor containing pyrophyllite and aluminium hydrate and intimately mixing the same with AI-O-OH hydroxy hydrogel network produced by flash condensation techniques. The active precursor on firing at a temperature in the range 1550°C to 1600°C provides mullite aggregates (of the order of 35% mullite) with dense microstructure. Dense mullite aggregate has industrial usage as a raw material for making different types of refractories, both shaped and unshaped, such as kiln furniture for use at temperatures less than 1400°C.